docs: Update Security Command Center UpdateNotificationConfig sample, adding filter to mutable field. (#2879)

* Update sample for UpdateNotificationConfig filter update flag

* fix syntax error

* docs: Update sample for UpdateNotificationConfig filter update flag

Author: hannah-tsai

securitycenter/src/main/java/com/google/cloud/examples/securitycenter/snippets/UpdateNotificationConfigSnippets.java

@@ -18,6 +18,7 @@
 
 // [START scc_update_notification_config]
 import com.google.cloud.securitycenter.v1.NotificationConfig;
+import com.google.cloud.securitycenter.v1.NotificationConfig.StreamingConfig;
 import com.google.cloud.securitycenter.v1.SecurityCenterClient;
 import com.google.protobuf.FieldMask;
 import java.io.IOException;
@@ -48,9 +49,13 @@ public static NotificationConfig updateNotificationConfig(
             .setName(notificationConfigName)
             .setDescription("updated description")
             .setPubsubTopic(pubsubTopic)
+            .setStreamingConfig(StreamingConfig.newBuilder().setFilter("state = \"ACTIVE\""))
             .build();
     FieldMask fieldMask =
-        FieldMask.newBuilder().addPaths("description").addPaths("pubsub_topic").build();
+        FieldMask.newBuilder()
+          .addPaths("description")
+          .addPaths("pubsub_topic")
+          .addPaths("streaming_config.filter").build();
 
     try (SecurityCenterClient client = SecurityCenterClient.create()) {
       NotificationConfig updatedConfig = client.updateNotificationConfig(configToUpdate, fieldMask);
@@ -60,4 +65,4 @@ public static NotificationConfig updateNotificationConfig(
     }
   }
   // [END scc_update_notification_config]
-}
+}